#include<iostream>
using namespace std;

void solve(){
	int n;
	cin>>n;
	int mid=n/2;
    for (int i = 0; i < n; i++) {
        if (n % 2 == 1 && i == mid) { 
            cout << "_";
        } else if (n % 2 == 0 && i == mid - 1) {
            cout << "_";
        } else {
            char tmp = 'a' + (i % 26); 
            cout << tmp;
        }
    }
	cout<<endl;
	return ;

} 

int main(){
	int t=1;
//	cin>>t;
	while(t--){
		solve();
	} 
	return 0;
} 
